Zhang Yalin, Zhao Wei-Min, Zhang Chunchen, Wang Peng, Wang Tong, Li Shao-Chun, Xing Zhongwen, Xing Dingyu
National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093, China.
Adv Mater. 2022 Feb;34(6):e2107799. doi: 10.1002/adma.202107799. Epub 2021 Dec 26.
The superconducting proximity effect (SPE) induces a superconductivity transition in otherwise non-superconducting thin films in proximity with a superconductor. The SPE usually occurs in real space and decays exponentially with film thickness. Herein, an abnormal SPE in a topological insulator (TI)/superconductor heterostructure is unveiled, which is attributed to the topologically protected surface state. Surprisingly, such abnormal SPE occurs in momentum space regardless of the TI film thickness, as long as the topological surface states are robust and form a continuous conduction loop. Combining transport measurements and scanning tunneling microscopy/spectroscopy techniques, the SPE in Bi Se /FeSe Te heterostructures is explored, where Bi Se is an ideal 3D topological insulator and FeSe Te a typical iron-based superconductor. As the thickness of the Bi Se thin film exceeds 400 nm, there still exists SPE-induced superconductivity on the surface of Bi Se thin film with a transition temperature T not less than 10 K. Such an extraordinary behavior is induced by the unique properties of topologically protected surface states of Bi Se . This research deepens the understanding of the important role of topologically protected surface states in the SPE.
超导邻近效应（SPE）会在与超导体相邻的原本非超导的薄膜中诱发超导转变。SPE通常发生在实空间中，并随薄膜厚度呈指数衰减。在此，我们揭示了拓扑绝缘体（TI）/超导体异质结构中的一种异常SPE，它归因于拓扑保护的表面态。令人惊讶的是，只要拓扑表面态稳健且形成连续的传导回路，这种异常SPE就会在动量空间中出现，而与TI薄膜的厚度无关。结合输运测量和扫描隧道显微镜/能谱技术，我们对Bi₂Se₃/FeSe₀.₅Te₀.₅异质结构中的SPE进行了研究，其中Bi₂Se₃是一种理想的三维拓扑绝缘体，FeSe₀.₅Te₀.₅是典型的铁基超导体。当Bi₂Se₃薄膜的厚度超过400纳米时，Bi₂Se₃薄膜表面仍存在由SPE诱发的超导性，其转变温度T不低于10 K。这种非凡的行为是由Bi₂Se₃拓扑保护表面态的独特性质所诱发的。这项研究加深了我们对拓扑保护表面态在SPE中重要作用的理解。
